Tapered optical fiber for coupling to diffused optical waveguides

ABSTRACT

An optical fiber having an endface with a D-shape at an endface. The optical fiber tapers from a round, cylindrical section to the D-shaped section so that adiabatic mode transformation is provided. Preferably, the D-shape is selected so that the optical fiber has a mode shape at its endface that matches the mode shape of a diffused waveguide.

RELATED APPLICATIONS

[0001] The present application claims the benefit of priority fromcopending provisional patent application No. 60/280,657 filed on Mar.30, 2001 and which is hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to fiber optics andoptical waveguides. More specifically, the present invention relates toa shaped optical fiber for providing efficient optical coupling to adiffused optical waveguide.

BACKGROUND OF THE INVENTION

[0003] Diffused optical waveguides typically have a D-shape, and, hence,a D-shaped optical mode. A D-shaped optical mode does not coupleefficiently to an optical fiber which has a circular optical mode.

SUMMARY

[0004] These objects and advantages are attained by an optical fiberhaving a shape that tapers from a conventional round shape, to aD-shape.

DESCRIPTION OF THE FIGURES

[0005] Informal drawings are filed herewith.

DETAILED DESCRIPTION

[0006] The present invention provides fibers that have a reducedcoupling loss when coupled to a D-shaped diffused waveguide. The opticalfibers of the present invention are compressed or polished so that theyhave an oval or D-shaped fiber core. Only the end portion of the opticalfiber is compressed. The compressed area of the fiber is tapered so thatlight in the fiber core experiences a roughly adiabatic modetransformation. The remaining fiber core had a D-shape, which providesimproved coupling to the diffused waveguide.

[0007] It will be clear to one skilled in the art that the aboveembodiment may be altered in many ways without departing from the scopeof the invention. Accordingly, the scope of the invention should bedetermined by the following claims and their legal equivalents.

What is claimed is:
 1. An optical fiber comprising: a) a cylindricalsection; b) an endface wherein the optical fiber has a D-shape at theendface; c) a tapered section disposed between the cylindrical sectionand the endface, wherein the tapered section has a flat side disposed atan angle with respect to a fiber axis.
 2. The optical fiber of claim 1wherein the angle is in the range of 0.01 to 5 degrees.
 3. The opticalfiber of claim 1 wherein the angle is in the range of 0.1 to 2 degrees.4. The optical fiber of claim 1 wherein the taper extends over a lengthin the range of 100-10000 microns.
 5. The optical fiber of claim 1wherein the taper extends over a length in the range of 300-3000microns.
 6. An optical communications device comprising: a) a diffusedoptical waveguide; b) an optical fiber coupled to the diffused opticalwaveguide, wherein the optical fiber comprises: 1) a cylindricalsection; 2) an endface wherein the optical fiber has a D-shape at theendface; 3) a tapered section disposed between the cylindrical sectionand the endface, wherein the tapered section has a flat side disposed atan angle with respect to a fiber axis.
 7. An optical fiber comprising:a) a cylindrical section with a round cross-section; b) an endfacewherein the optical fiber has a D-shape cross-section at the endface; c)a tapered section disposed between the cylindrical section and theendface, wherein the tapered section comprises a smooth transitionbetween the cylindrical section and the D-shape.
 8. The optical fiber ofclaim 7 wherein the tapered section is formed by polishing.
 9. Theoptical fiber of claim 7 wherein the tapered section is formed by heatand compression.